Coil support



Feb. 14, 1950 D. BOTERWEG 2,497,204

con. SUPPORT Filed July 20, 1946 DIRK 302513171156.

' I NV EN TOR.

Patented Feb. 14, 1950 COIL SUPPORT Dirk Boterweg, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford Conn., as trustee Application July 20, 1946, Serial No. 685,138 In the Netherlands August 25, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires August 25, 1963 4 Claims. 1

This invention relates to a coil constituted by an electric conductor which extends in a plane of straight lines and whose turns cross the straight lines on that plane, said conductor being supported by at least two insulating supporting rods parallel to these straight lines.

This kind of coils comprises cylindrical, conical and prismatic coils and coils whose turns are located on a hyperboloid of revolution.

With coils of this kind it is necessary for the turns of the wound conductor to be so supported as to be insulated from one another. In known constructions the wound conductor is some times arranged on a coil base of insulating material. In this case a comparatively large amount of insulating material is present in the field of the coil, leading to losses at high frequencies. Also from a point of view of natural capacity it is important to utilize as small an amount of insulating material as possible. In another known construction the turns of the wound conductor are fastened to insulating supporting rods which are arranged in parallel with the axis of the coil and which are spaced apart themselves by means of terminal plates arranged on each side. In this case the fastening of the turns to the supporting rods may have been effected in different manners, for example by making parts of the supporting rods silver-plated and soldering the turns to them. It is also known to solder or topoint-weld the turns to sleeve-shaped metal parts clamped on the supporting rod or to contraction spirals wound on these supporting rods. In the latter construction it is a drawback that close to the point where the field of the coil is strongest there are arranged short-circuited turns acting upon the inductance and increasing the losses due to the short-circuit currents produced in the turns.

The present invention provides a novel construction by which the said drawbacks are obviated and at the same time other advantages may be obtained.

The construction of the coil according to the invention has the characteristic that the turns of the coil are stretched against the supporting rods. As will further appear from the constructional examples shown in the drawing, this construction offers considerable advantages. It can immediately be ascertained that the most advantageous arrangement of the coils on rods, which is known per se, can be maintained whereas the connection hitherto used for each or for a great number of the turns directly to the rods can be dispensed with, thus also avoiding the drawbacks involved thereby.

The coils according to the invention excel by simple, compact, strong and inexpensive construction whilst exhibiting excellent electrical properties.

In an advantageous form of construction according to the invention, two supporting rods are located on the same side of the coil and are spaced apart through a distance smaller than half the average diameter of the coil while the turns are pulled against these rods by means of a draw connection engaging, on the one hand, the portion of the turn located between the rods and, on the other hand, a bridge piece arranged on the other side of the rods. Now, it appears to be possible with the use of but two supporting rods thus to obtain a very strong support for the turns, so

that a stable assembly is obtained. Since but In an advantageous form of construction of the inductance according to the invention the two supporting rods are located outside the coil. As a rule, the field is there weaker than at the interior of the coil, resulting in an additional decrease of losses. In addition, it is rendered possible to construct a highly compact adjustable inductance by arranging inside the coil a sliding contact capable of sliding along the turns. During the movement of this sliding contact no trouble is experienced from the supporting rods located outside the coil.

The draw connection is preferably constituted by a screw. In this case it may be easily loosened so that it is possible for the construction to be slightly modified after mounting. Especially the pitch of the coil may be varied by moving the turns along the supporting rods after the draw connections have been loosened. It is evident that this movement, if not desired, may be prevented by providing the supporting rods with notch-shaped depressions in which bear the turns.

In another advantageous form of construction according to the invention the draw connection engages a tension strip surrounding the turn. In

this case it is possible for the turn to be rotated with respect to the supporting rods.

In still another advantageous form of construction of the coil according to the invention at least one supporting rod is adjustable towards the turns. Now, the turns can be sufficiently supported by the supporting rods without any additional fastening means. To this end, the supporting rods are displaced towards the turns to such an extent that any clearance is suppressed and the windings engage the supporting rods. The friction thus involved avoids lateral displacement of the turns along the rods. If this frictional force is not sufficient for the purpose, the rod may be provided with notches, grooves or depressions in which bear the turns. In some cases it also sufiices to roughen the surfaces of the supporting rods.

In an advantageous construction of a prismatic coil according to the invention the insulating rods placed outside the prism are parallel with and between subsequent edges of the prism. To remove the amount of play in the dimensions of the various turns use is made of the resilience which occurs in a straightpiece of wire when located in the middle.

In an advantageous form of construction of the cylindrical coil according to the invention the supporting rods are spaced apart through equal distances on the circumference of the cylinder, thus resulting in a simple symmetrical construction. It is frequently of importance that as little insulating material as possible should be brought into the vicinity of the turns. Consequently, if possible, the minimum-number of supporting rods is used. With coils of not too large size only three supporting rods suffice.

In another advantageous form of construction of a coil according to the invention two supprting rods are arranged outside the coil and one supporting rod is arranged inside the coil between the two others. It is thus possible to bring the three supporting rods close to one another so that a large portion of the circumference of the turns is free.

In an advantageous form of construction of a mutual inductance constituted by two coils, coaxially arranged, according to the invention, the supporting rods of the inner coil are arranged at the interior and those of the outer coil are arranged at the exterior. It is thus possible to bring the turns of the two coils very close to each other.

In order that the invention may be more clearly understood and readily carried into effect it will now be described more fully with reference to the accompanying drawings.

Figs. 1 and 2 show details of inductances according to, the invention.

Figs. 3 and 4 show inductances realised in accordance with the invention.

Figs. 5 and 6 illustrate diagrammatically other possibilities.

Fig. 1 shows a portion of the two supporting rods and 2 which in this case are of ceramic material and have a circular section. The portion 3 located between the two rods of the turn 4 of the conductor otherwise not shown comprises a clamping strip 5. On the other side of the rods and 2 is arranged the bridge-piece 6. The draw connection, due to which according to the invention the turns are pulled iast against the supporting rods, is in this case constituted by the screw 1 arranged between the bridge-piece 6 and the clamping strip 5. It is evident that by tight ening thescrew the turn 4 can be pushed in the direction P through the clamping strip and in the direction Q along the supporting rods I and 2. The latter movement may be avoided,

if desired, by means of depressions provided at the back of the rods and in which bear the turns.

Fig. 2 shows a similar mode of fastening of the turn It] to the supporting rods H and I2. In this case the screw 3, on the one hand, acts upon the bridge piece M and, on the other hand, engages a threaded hole provided in the turn I0. In this case the displacement corresponding to P of Fig. 1 is limited by the length of the slot IS in the bridge piece M.

The bridge pieces 6 and I5 shown in Figs. 1 and 2 are constituted by metal strips in such a manner that the forces to be received, as can be seen in the figures, fall in the direction of the largest transverse dimension. It is thus possible to support the tensile force required for clamping the turns whilst using a minimum quantity of material. This is advantageous in view of the losses. As it appears from the figures, no shortcircuited turns are present at the points of fastening of the turns. This would be the case, however, if the turns were soldered to sleeves or contraction spirals entirely surrounding each supporting rod.

The coil shown in Fig. 3 is composed of a wound conductor 20. According to the invention, its turns are supported by the two supporting rods 2| and 22 having a mutual distance smaller than half the average diameter of the coil. The turns are pulled against the rods by means of draw connections 23 which correspond to those of Fig. 2. The two rods 2| and 22 are spaced apart by the terminal pieces 24 and 25 arranged on each side of the coil. In some cases one terminal piece suffices, amongst others for easily pushing-in a coupling coil. In this case the rods 2| and 22 are not provided with depressions so that the turns of the conductor 20 bear against the outer surfaces of these rods. It is thus possible in a very simple manner to adjust the inductance of the coil within comparatively broad limits by means of a displacement of the turns along the rods. This may be effected, for example, by bending according to requirements the straight portion 26 of the conductor 2|], the turns of the two portions of the coil thus being brought towards each other.

The coil shown in Fig. 4 is constituted by a helically wound electric conductor 3| of metal wire, tube, or strip, which is supported by the supporting rods 32, 33, 34 and 35. These are arranged outside the turns and are secured in metal terminal pieces 35 and 31. The extremities of the supporting rods comprise square metal parts 38 which can be moved in the grooves 39 by means of the screws 40 towards the turns of the coil, that is to say in this case to the interior. Thus, the turns of the coil may be clamped between the supporting rods. In this case the supporting rods are of ceramic material and have a circular section. In the construction shown, the supporting rods are not provided with grooves. Consequently, the turns engage the cylindrical surfaces of the supporting rods, thus giving the advantage that during mounting and, if desired, also afterwards the pitch of the coil with which the axis of the conductor is in coincidence may be easily varied by unscrewing the adjusting screws 40 of the supporting rods to such an extent that the turns may be displaced along the supporting rods. In the construction shown, particular methods known per se have still been taken in order to avoid the displacement of the metal parts 38 in the longitudinal direction of the supporting rods with respect to the terminal pieces 36 and 31. For example, on each side of the terminal pieces little plates may be arranged on the metal parts 38, embracing the edges of the groove 39. The terminal plates are thus also spaced apart through the required distance by the supporting rods, an additional constructional connection of the terminal pieces 35 and 31 being superfluous. By means of slight unimportant modifications the construction shown may also serve for conical and prismatic coils and for coils whose turns extend on the surface of a hyperboloid of revolution. However, in this case it will as a rule be necessary to provide the supporting rods with incisions or grooves, in order to avoid the displacement of the turns.

Fig. 5 shows a cylindrical coil of which each turn 50 is held by three supporting rods 5|, 52 and 53. In this case the two supporting rods 5| and 52 are located outside the coil, whereas the supporting rod 53 is located inside the coil. The rod 53 is adjustable with respect to the rods 5| and 52 in the direction P. As can be seen from the figure, a large portion of the circumference of the turns is free. This form of construction has the advantage amongst others that the rods 5|, 52 and 53 can be arranged wholl or substantially wholly in a flat plane.

Fig. 6 shows a turn 60 of a prismatic coil having a hexagonal shape. The three supporting rods 6|, 62 and 63 are arranged in parallel with and between subsequent edges of the prism, which in this case are normal to the plane of drawing. It is thus possible for several turns of a somewhat too large size to be deformed by depression of the sides in such a manner that at last all the turns of the coil engage the supporting rods.

What I claim is:

1. An inductance coil comprising an electric conductor wound in adjacent spaced convolutions whose outer edges fall in a cylindrical surface generated by a straight line, a pair of insulating support rods arranged parallel to the line in one of its positions and serving to support the wound conductor, the rods being located on the same side of the coil and spaced apart by a distance smaller than half the average diameter of the coil, and means for securing individual convolutions of said conductor against the rods to prevent peripheral or transverse movement of a convolution relative to the rods cmprising a draw element acting on the arc of the convolution between the support rods, a bridge element disposed on the opposite sides of the support rods, and an adjustable element for connecting the draw element and the bridge element with an adjustable tension.

2. An inductance coil comprising an electric conductor wound in adjacent spaced convolutions whose outer edges fall in a cylindrical surface generated by a straight line, a pair of insulating support rods arranged parallel to the line in one of its positions and serving to support the wound conductor, the rods being located on the same side of the coil and spaced apart by a distance smaller than half the average diameter of the coil, and means for securing individual convolutions of said conductor against the rods to prevent peripheral or transverse movement of a convolution relative to the rods comprising a draw element acting on the arc of the convolution between the support rods, a bridge element disposed on the opposite sides of the support rods, and an adjustable element for connecting the draw element and the bridge element with adjustable tension, the adjustable element embodying a threaded screw with a slotted head for easy adjustment.

3. An inductance coil comprising an electric conductor wound in adjacent spaced convolutions whose outer edges fall in a cylindrical surface generated by a straight line, a pair of insulating support rods arranged parallel to the line in one of its positions and serving to support the wound conductor, the rods being located on the same side of the coil and spaced apart by a distance smaller than half the average diameter of the coil, and means for securing individual convolutions of said conductor against the rods to prevent peripheral or transverse movement of a convolution relative to the rods comprising a draw element acting on the arc of the convolution between the support rods, a bridge element disposed on the opposite sides of the support rods, and an adjustable element for connecting the draw element and the bridge element with adlustable tension, the draw element embodying a thin saddle strip closely surrounding the side of the convolution opposite the rods.

4. An inductance coil comprising an electric conductor wound in adjacent spaced convolutions whose outer edges fall in a cylindrical surface generated by a straight line, a pair of insulating support rods arranged parallel to the line in one of its positions and serving to support the wound conductor, the rods being located on the same side of the coil and spaced apart by a distance smaller than half the average diameter of the coil, and means for securing individual convolutions of said conductor against the rods to prevent peripheral or transverse movement of a convolution relative to the rods comprising a draw element acting on the arc of the convolution between the support rods, a bridge element disposed on the opposite sides of the support rods, and an adjustable element for connecting the draw element and the bridge element with adjustable tension in which the bridge element constitutes a double cantilever between the two rods.

DIRK BOTERWEG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,540,514 Cote June 2, 1925 1,625,212 Karas Apr. 19, 1927 1,891,481 Scofield Dec. 20, 1932 2,331,384 Flachowsky Oct. 12, 1943 FOREIGN PATENTS Number Country Date 586,479 France Jan. 6, 1925 379,310 Great Britain Aug. 26, 1932 

